Flooded native pastures of the northern region of the Pantanal of Mato Grosso: biomass and primary productivity variations.

The Pantanal comprises a number of landscape units, submitted to a flood pulse with variable intensity or regularity. One of these units, the flooded plains, is important in cattle raising. This study was carried out in the northern portion of the Pantanal and presents data related to the productive dynamics of the flooded native pastures both protected from and exposed to cattle. The greatest total biomass values were for the protected pasture due to accumulated dead biomass. Net primary production presented smaller values at the flood-season start and increasing gradually beginning in the subsequent rainy season. However, consumption by cattle was also more intense during the months of greater precipitation. The effect of cattle in pastures is of fundamental importance to management since it prevents the dead biomass excess that increases fire risks.     

Renal oncocytoma: origin from the collecting duct

The histo- and cytogenesis of two cases of renal oncocytoma have been studied by cytomorphological and cytochemical methods. Transitions from collecting ducts into oncocytic tubules were observed at the light and electron microscopic levels. The fine structure of the oncocytes in tubules and tumors is described in detail. Cytochemically, the oncocytic tubules and oncocytomas share many characteristics with the distal nephron, especially the collecting ducts. A striking difference is the enhanced activity of succinic dehydrogenase which corresponds to the increase in the number of mitochondria in oncocytes. All the results suggest that renal oncocytoma originates from the collecting duct.     

The cytotaxonomy ofEmilia spp. (Asteraceae: Senecioneae) occurring in Brazil

Analysis of several populations in a large part of the distribution area of the genusEmilia in Brazil has revealed only two species: the diploidE. sonchifolia and the tetraploidE. fosbergii. The more widely reportedE. coccinea was not found. They show a karyotype constancy in morphology and chromosome number (2n = 10 and 2n = 20, respectively), C-banding pattern and number of secondary constrictions. Some indications were found thatE. fosbergii may be an allopolyploid and that its ancestors had different genome sizes.     

Histopathology of experimental Aspergillus fumigatus keratitis

Histopathological studies in rabbit's eyes, 7 and 14 days after intracorneal inoculation with 1×10⁵ Aspergillus fumigatus conidia have been performed.Similar lesions were found in both periods with fungal hyphae in the anterior third of corneal stroma, round cell infiltration from the sclero-corneal edge and in the anterior chamber and, neovascularization.No lesions were found in the Descemet's membrane.Gomori silver-methenamine stain with hematoxiline-eosine counter-stain was found to be the most reliable stain to detect fungal presence in corneal stroma, and Masson's trichromic stain in the study of pathological changes in ocular elements.     

Gating properties of channels formed by colicin Ia in planar lipid bilayer membranes

Summary Colicin Ia forms voltage-dependent channels when incorporated into planar lipid bilayers. A membrane containing many Colicin Ia channels shows a conductance which is turned on when high positive voltages (>+10 mV) are applied to thecis side (side to which the protein is added). The ionic current flowing through the membrane in response to a voltage step shows at first an exponential and then a linear rise with time. The relationship between the steady-state conductance, achieved immediately after the exponential portion, and voltage is S-shaped and is adequately fit by a Boltzmann distribution. The time constant () of the exponential is also dependent on voltage, and the relation between these two parameters is asymmetric aroundV _o (voltage at which half of the channels are open). In both cases the steepness of the voltage dependence, a consequence of the number of effective gating particles (n) present in the channel, is greatly influenced by the pH of the bathing solutions. Thus, increasing the pH leads to a reduction inn, while acidic pH's have the opposite effects. This result is obtained either by changing the pH on both sides of the membrane or on only one side, be itcis orrans. On the other hand, changing pH on only one side by addition of an impermeant buffer fails to induce any change inn. At the single-channel level, pH had an effect both on the unitary conductance, doubling it in going from pH 4.5 to 8.2, as well as on the fraction of time the channels stay open,F _(v). For a given voltage,F _(v) is clearly diminished by increasing the pH. This titration of the voltage sensitivity leads to the conclusion that gating in the Colicin Ia molecule is accomplished by charged amino-acid residues present in the protein molecule. Our results also support the notion that these charged groups are inside the aqueous portion of the channel.     

Chemotherapy of Aspergillus fumigatus keratitis: An experimental study

An experimental Keratitis study of Aspergillus fumigatus was performed in 130 rabbits divided into 12 groups of ten animals each. Three antifungal drugs (myconazole, amphotericin B and pimaricin) were tested using two procedures (topical drops and subconjunctival injections) and two different concentrations (500 and 10 000 times the MIC). In each case, the drugs were applied every 3 h starting 14 h after inoculation. Miconazole was useful at 10 mg/ ml concentration by topical drops and subconjunctival injections, but was less useful at 5 mg/ ml. Amphotericin B was useful at 5 mg/ ml concentration by topical drops and less useful at 2 mg/ ml.No differences were found between the two concentrations by subconjunctival administration. Pimaricin was useful by topical drops at 50 mg/ ml concentration and less useful at 10 mg/ ml as well as by subconjunctival injections.     

Identification of a frameshift mutation responsible for the silent phenotype of human serum cholinesterase, Gly 117 (GGT----GGAG).

A frameshift mutation that causes a silent phenotype for human serum cholinesterase was identified in the DNA of seven individuals of two unrelated families. The mutation, identified using the polymerase chain reaction, causes a shift in the reading frame from Gly 117, where GGT (Gly)----GGAG (Gly+ 1 base) to a new stop codon created at position 129. This alteration is upstream of the active site (Ser 198), and, if any protein were made, it would represent only 22% of the mature enzyme found in normal serum. Results of analysis of the enzymatic activities in serum agreed with the genotypes inferred from the nucleotide sequence. Rocket immunoelectrophoresis using alpha-naphthyl acetate to detect enzymatic activity showed an absence of cross-reactive material, as expected. One additional individual with a silent phenotype did not show the same frameshift mutation. This was not unexpected, since there must be considerable molecular heterogeneity involved in causes for the silent cholinesterase phenotype. This is the first report of a molecular mechanism underlying the silent phenotype for serum cholinesterase. The analytical approach used was similar to the one we recently employed to identify the mutation that causes the atypical cholinesterase variant.     

Vicariance and endemism in a Neotropical savanna hotspot: distribution patterns of Cerrado squamate reptiles

Aim To test predictions of the vicariance model, to define basic biogeographical units for Cerrado squamates, and to discuss previous biogeographical hypotheses. Location Cerrado; South American savannas south of the Amazon, extending across central Brazil, with marginal areas in Bolivia and Paraguay and isolated relictual enclaves in adjacent regions. Methods We compiled species occurrence records via field sampling and revision of museum specimens and taxonomic literature. All species were mapped according to georeferenced locality records, and classified as (1) endemic or non‐endemic, (2) typical of plateaus or depressions, and (3) typical of open or forested habitats. We tested predictions of the vicariance model using biotic element analysis, searching for non‐random clusters of species ranges. Spatial congruence of biotic elements was compared with putative areas of endemism revealed by sympatric restricted‐range species. Effects of topographical and vegetational mosaics on distribution patterns were studied according to species composition in biotic elements and areas of endemism. Results We recorded 267 Cerrado squamates, of which 103 (39%) are endemics, including 20 amphisbaenians (61% endemism), 32 lizards (42%) and 51 snakes (32%). Distribution patterns corroborated predictions of the vicariance model, revealing groups of species with significantly clustered ranges. An analysis of endemic species recovered seven biotic elements, corroborating results including non‐endemics. Sympatric restricted‐range taxa delimited 10 putative areas of endemism, largely coincident with core areas of biotic elements detected with endemic taxa. Distribution patterns were associated with major topographical and vegetational divisions of the Cerrado. Endemism prevailed in open, elevated plateaus, whereas faunal interchange, mostly associated with forest habitats, was more common in peripheral depressions. Main conclusions Our results indicate that vicariant speciation has strongly shaped Cerrado squamate diversity, in contrast to earlier studies emphasizing faunal interchange and low endemism in the Cerrado vertebrate fauna. Levels of squamate endemism are higher than in any other Cerrado vertebrate group. The high number of recovered endemics revealed previously undetected areas of evolutionary relevance, indicating that biogeographical patterns in the Cerrado were poorly represented in previous analyses. Although still largely undocumented, effects of vicariant speciation may be prevalent in a large fraction of Cerrado and Neotropical biodiversity.     

Gibberellin reverses the negative effect of paclobutrazol but not of chlorocholine chloride on the expression of SGs/GAs biosynthesis-related genes and increases the levels of relevant metabolites in Stevia rebaudiana

Plant Cell, Tissue and Organ Culture (PCTOC) - Steviol glycosides (SGs) and gibberellins (GAs) share the same molecular basis. However, the coordination of their respective biosynthetic pathways is...